After centuries of 'controlling' land, Gulf learns who's the boss

The Gulf Coast has always been vulnerable to coastal storms, but over the years people have made things worse, particularly in Louisiana, where Hurricane Katrina struck yesterday. Since the 18th century, when French colonial administrators required land claimants to establish ownership by building levees along bayous, streams and rivers, people have been trying to dominate the region's landscape and the forces of its nature.

As long as people could control floods, they could do business. But, as people learned too late, the landscape of South Louisiana depends on floods: it is made of loose Mississippi River silt, and the ground subsides as this silt consolidates. Only regular floods of muddy water can replenish the sediment and keep the landscape above water. But flood control projects channel the river's nourishing sediment to the end of the birdfoot delta and out into the deep water of the Gulf of Mexico.

Although early travelers realized the irrationality of building a port on shifting mud in an area regularly ravaged by storms and disease, the opportunities to make money overrode all objections.

When most transport was by water, people would of course settle along the Mississippi River, and of course they would build a port city near its mouth. In the 20th century, when oil and gas fields were developed in the gulf, of course people added petrochemical refineries and factories to the river mix, convenient to both drillers and shippers. To protect it all, they built an elaborate system of levees, dams, spillways and other installations.

As one 19th-century traveler put it, according to Ari Kelman, an environmental historian at the University of California, Davis, "New Orleans is surprising evidence of what men will endure, when cheered by the hopes of an ever-flowing tide of dollars and cents."